This invention relates to a pneumatic punch for paper, and more particularly to a pneumatic punch useful in punching holes in photographic paper, a step frequently used in modern day photograph printing techniques. In the photograph printing method described and illustrated in U.S. Pat. No. 3,807,855, of Zajack, issued Apr. 30, 1974, a photograph printing machine is provided in which images from negatives are sequentially exposed onto consecutive segments of a roll of photograph print paper. Holes are punched in the print paper to differentiate between individual photographs and between photographs from different rolls of negatives. These holes activate a cutter mechanism at the appropriate location along the roll of print paper, so that the developed photographs may be automatically cut. They are usually located between adjacent prints so that they can be removed by the cutter mechanism.
The punches used in such method and apparatus have usually been heavy, solenoid operated punches. The solenoid, because of its size and the nature of its firing action, causes vibrations in the frame such that the punch step can take place only after or before, and not during, exposure of the photographic paper to the image from the negative. In one such punch, to the free end of the solenoid is attached a plate-like device from which extends a punch of square cross-section. The punch is constrained to move longitudinally in a slot along the outside of the body of a die, with the punch itself being positioned to cooperate with a corresponding rectangular shaped slot in a die button secured to the die body. The slot in the die button extends into an aperture in the die body, beneath which aperture a current of air passes to blow slugs to a location remote from that of the punching operation. Such a prior art device has presented many problems of maintenance. The solenoid has to be replaced from time-to-time. The alignment of the punch and die button so that the punch will operate properly (which is required for example if the punch becomes out of alignment of a punch or die button is replaced) usually requires the services of an expert since alignment must be extremely precise. Another problem with such prior art device is that the pressure under which the punch is operated cannot be increased or decreased without actually modifying the punch, for example, by replacing the solenoid. It should be noted, with respect to such prior art punches, that they are returned to ready position after each punch, under urging of the spring acting on the punch mechanism.
Other prior art pneumatic punches of background interest are those described and illustrated in Coombes U.S. Pat. No. 3,939,743 issued Feb. 24, 1976 and Goldman U.S. Pat. No. 3,524,368. Again in these punches alignment of punch and die buttons requires great care and skill, since the elements of the punch are separately mounted on supports.
Also of general background interest is Bouchard French Pat. No. 1,147,947 granted June 17, 1957. This patent describes and illustrates an hydraulic punch press, the device being operated by a system of liquid reservoirs communicating with each other through valved passageways.
Another punch device of general background interest is described and illustrated in Daniel Canadian Pat. No. 723,969 issued Dec. 21, 1965.
It is an object of the present invention to provide a pneumatic punch which will be effective for use in punching photographic or other types of paper. It is a further object of the present invention to provide such a punch which can simultaneously provide pneumatic ejection of chips or slugs from the work area. It is a further object of the invention to provide a small, lightweight easily manufacturable and servicable punch, which can operate quickly and effectively in association with apparatus for developing photographic prints on strips of photographic paper.